The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119][RFC8174] when, and only when, they appear in all capitals, as shown here.

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In Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS), a Traffic Engineering Database (TED) is used in computing paths for connection oriented packet services and for circuits. The TED contains all relevant information that a Path Computation Element (PCE) needs to perform its computations. It is important that the TED be complete and accurate each time, the PCE performs a path computation.

In MPLS and GMPLS, interior gateway routing protocols (IGPs) have been used to create and maintain a copy of the TED at each node running the IGP. One of the benefits of the PCE architecture [RFC4655] is the use of computationally more sophisticated path computation algorithms and the realization that these may need enhanced processing power not necessarily available at each node participating in an IGP.

Section 4.3 of [RFC4655] describes the potential load of the TED on a network node and proposes an architecture where the TED is maintained by the PCE rather than the network nodes. However, it does not describe how a PCE would obtain the information needed to populate its TED. PCE may construct its TED by participating in the IGP ([RFC3630] and [RFC5305] for MPLS-TE; [RFC4203] and [RFC5307] for GMPLS). An alternative is offered by BGP-LS [RFC7752] .

[RFC8231] describes a set of extensions to PCEP to provide stateful control. A stateful PCE has access to not only the information carried by the network's Interior Gateway Protocol (IGP), but also the set of active paths and their reserved resources for its computations. PCC can delegate the rights to modify the LSP parameters to an Active Stateful PCE. This requires PCE to quickly be updated on any changes in the Topology and TEDB, so that PCE can meet the need for updating LSPs effectively and in a timely manner. The fastest way for a PCE to be updated on TED changes is via a direct interface with each network node and with incremental update from each network node with only the attribute that is modified.

[RFC8281] describes the setup, maintenance and teardown of PCE-initiated LSPs under the stateful PCE model, without the need for local configuration on the PCC, thus allowing for a dynamic network that is centrally controlled and deployed. This model requires timely topology and TED update at the PCE.

[RFC5440] describes the specifications for the Path Computation Element Communication Protocol (PCEP). PCEP specifies the communication between a Path Computation Client (PCC) and a Path Computation Element (PCE), or between two PCEs based on the PCE architecture [RFC4655].

This document describes a mechanism by which Link State and TE information can be collected from networks and shared with PCE using the PCEP itself. This is achieved using a new PCEP message format. The mechanism is applicable to physical and virtual links as well as further subjected to various policies.

A network node maintains one or more databases for storing link-state and TE information about nodes and links in any given area. Link attributes stored in these databases include: local/remote IP addresses, local/ remote interface identifiers, link metric and TE metric, link bandwidth, reservable bandwidth, per CoS class reservation state, preemption and Shared Risk Link Groups (SRLG). The node's PCEP process can retrieve topology from these databases and distribute it to a PCE, either directly or via another PCEP Speaker, using the encoding specified in this document.

Further [RFC6805] describes Hierarchical-PCE architecture, where a parent PCE maintains a domain topology map. To build this domain topology map, the child PCE can carry the border nodes and inter-domain link information to the parent PCE using the mechanism described in this document. Further as described in [I-D.ietf-pce-applicability-actn], the child PCE can also transport abstract Link-State and TE information from child PCE to a Parent PCE using the mechanism described in this document to build an abstract topology at the parent PCE.

[RFC8231] describe LSP state synchronization between PCCs and PCEs in case of stateful PCE. This document does not make any change to the LSP state synchronization process. The mechanism described in this document are on top of the existing LSP state synchronization.

Where there is no IGP or BGP-LS running at the PCE to learn link-state and TE information.

Where there is IGP or BGP-LS running but with a need for a faster and direct TE and link-state population and convergence at the PCE.

A PCE may receive partial information (say basic TE, link-state) from IGP and other information (optical and impairment) from PCEP.

A PCE may receive an incremental update (as opposed to the entire information of the node/link).

A PCE may receive full information from both existing mechanism (IGP or BGP) and PCEP.

Where there is a need for transporting (abstract) Link-State and TE information from child PCE to a Parent PCE in H-PCE [RFC6805]; as well as for Provisioning Network Controller (PNC) to Multi-Domain Service Coordinator (MDSC) in Abstraction and Control of TE Networks (ACTN) [RFC8453].

Where there is an existing PCEP session between all the nodes and the PCE-based central controller (PCECC) [RFC8283], and the operator would like to use PCEP as a direct south bound interface to the all the nodes in the network. This enables operator to use PCEP as single direct protocol between the controller and all the nodes in the network. In this mode all nodes send the only local information.

Based on the local policy and deployment scenario, a PCC chooses to send only local information or both local and remote learned information.

How a PCE manages the link-state (and TE) information is implementation specific and thus out of scope of this document.

The prefix information in PCEP-LS can also help in determining the domain of the endpoints in H-PCE (and ACTN). Section 4.5 of [RFC6805] describe various mechanism and procedures that might be used, PCEP-LS provides a simple mechanism to exchange this information within PCEP. [RFC8453] defines three types of topology abstraction - (1) Native/White Topology; (2) Black Topology; and (3) Grey Topology. Based on the local policy, the PNC (or child PCE) would share the domain topology to the MDSC (or Parent PCE) based on the abstraction type. The protocol extention defined in this document can carry any type of topology abstraction.

Following key requirements associated with link-state (and TE) distribution are identified for PCEP:

The PCEP speaker supporting this draft MUST be a mechanism to advertise the Link-State (and TE) distribution capability.

PCC supporting this draft MUST have the capability to report the link-state (and TE) information to the PCE. This MUST includes self originated information and also allow remote information learned via routing protocols. PCC MUST be capable to do the initial bulk sync at the time of session initialization as well as changes after.

A PCE MAY learn link-state (and TE) from PCEP as well as from existing mechanism like IGP/BGP-LS. PCEP extension MUST have a mechanism to link the information learned via other means. There MUST NOT be any changes to the existing link-state (and TE) population mechanism via IGP/BGP-LS. PCEP extension SHOULD keep the properties in a protocol (IGP or BGP-LS) neutral way, such that an implementation may not need to know about any OSPF or IS-IS or BGP protocol specifics.

It SHOULD be possible to encode only the changes in link-state (and TE) properties (after the initial sync) in PCEP messages. This leads to faster convergance.

The same mechanism should be used for both MPLS TE as well as GMPLS, optical and impairment aware properties.

The same mechanism should be used for PCE to PCE Link-state (and TE) synchronization.

Several new functions are required in PCEP to support distribution of link-state (and TE) information. A function can be initiated either from a PCC towards a PCE (C-E) or from a PCE towards a PCC (E-C). The new functions are:

Capability advertisement (E-C,C-E): both the PCC and the PCE MUST announce during PCEP session establishment that they support PCEP extensions for distribution of link-state (and TE) information defined in this document.

Link-State (and TE) synchronization (C-E): after the session between the PCC and a PCE is initialized, the PCE must learn Link-State (and TE) information before it can perform path computations. In case of stateful PCE it is RECOMENDED that this operation be done before LSP state synchronization.

In this document, we define a new PCEP messages called LS Report (LSRpt), a PCEP message sent by a PCC to a PCE to report link-state (and TE) information. Each LS Report in a LSRpt message can contain the node or link properties. An unique PCEP specific LS identifier (LS-ID) is also carried in the message to identify a node or link and that remains constant for the lifetime of a PCEP session. This identifier on its own is sufficient when no IGP or BGP-LS running in the network for PCE to learn link-state (and TE) information. Incase PCE learns some information from PCEP and some from the existing mechanism, the PCC SHOULD include the mapping of IGP or BGP-LS identifier to map the information populated via PCEP with IGP/BGP-LS. See Section 8.1 for details.

During PCEP Initialization Phase, PCEP Speakers (PCE or PCC) advertise their support of LS (and TE) distribution via PCEP extensions. A PCEP Speaker includes the "LS Capability" TLV, described in Section 9.2.1, in the OPEN Object to advertise its support for PCEP-LS extensions. The presence of the LS Capability TLV in PCC's OPEN Object indicates that the PCC is willing to send LS Reports whenever local link-state (and TE) information changes. The presence of the LS Capability TLV in PCE's OPEN message indicates that the PCE is interested in receiving LS Reports whenever local link-state (and TE) information changes.

The PCEP extensions for LS (and TE) distribution MUST NOT be used if one or both PCEP Speakers have not included the LS Capability TLV in their respective OPEN message. If the PCE that supports the extensions of this draft but did not advertise this capability, then upon receipt of a LSRpt message from the PCC, it SHOULD generate a PCErr with error-type 19 (Invalid Operation), error-value TBD1 (Attempted LS Report if LS capability was not advertised) and it will terminate the PCEP session.

The LS reports sent by PCC MAY carry the remote link-state (and TE) information learned via existing means like IGP and BGP-LS only if both PCEP Speakers set the R (remote) Flag in the "LS Capability" TLV to 'Remote Allowed (R Flag = 1)'. If this is not the case and LS reports carry remote link-state (and TE) information, then a PCErr with error-type 19 (Invalid Operation) and error-value TBD1 (Attempted LS Report if LS remote capability was not advertised) and it will terminate the PCEP session.

The purpose of LS Synchronization is to provide a checkpoint-in- time state replica of a PCC's link-state (and TE) data base in a PCE. State Synchronization is performed immediately after the Initialization phase (see [RFC5440]). In case of stateful PCE ([RFC8231]) it is RECOMENDED that the LS synchronization should be done before LSP state synchronization.

During LS Synchronization, a PCC first takes a snapshot of the state of its database, then sends the snapshot to a PCE in a sequence of LS Reports. Each LS Report sent during LS Synchronization has the SYNC Flag in the LS Object set to 1. The end of synchronization marker is a LSRpt message with the SYNC Flag set to 0 for an LS Object with LS-ID equal to the reserved value 0. If the PCC has no link-state to synchronize, it will only send the end of synchronization marker.

Either the PCE or the PCC MAY terminate the session using the PCEP session termination procedures during the synchronization phase. If the session is terminated, the PCE MUST clean up state it received from this PCC. The session re-establishment MUST be re-attempted per the procedures defined in [RFC5440], including use of a back-off timer.

If the PCC encounters a problem which prevents it from completing the LS synchronization, it MUST send a PCErr message with error-type TBD2 (LS Synchronization Error) and error-value 2 (indicating an internal PCC error) to the PCE and terminate the session.

The PCE does not send positive acknowledgments for properly received LS synchronization messages. It MUST respond with a PCErr message with error-type TBD2 (LS Synchronization Error) and error-value 1 (indicating an error in processing the LSRpt) if it encounters a problem with the LS Report it received from the PCC and it MUST terminate the session.

The LS reports can carry local as well as remote link-state (and TE) information depending on the R flag in LS capability TLV.

The PCC MUST report any changes in the link-state (and TE) information to the PCE by sending a LS Report carried on a LSRpt message to the PCE. Each node and Link would be uniquely identified by a PCEP LS identifier (LS-ID). The LS reports may carry local as well as remote link-state (and TE) information depending on the R flag in LS capability TLV. In case R flag is set, It MAY also include the mapping of IGP or BGP-LS identifier to map the information populated via PCEP with IGP/BGP-LS.

A permanent PCEP session MUST be established between a PCE and PCC supporting link-state (and TE) distribution via PCEP. In the case of session failure, session re-establishment MUST be re-attempted per the procedures defined in [RFC5440].

As defined in [RFC5440], a PCEP message consists of a common header followed by a variable-length body made of a set of objects that can be either mandatory or optional. An object is said to be mandatory in a PCEP message when the object must be included for the message to be considered valid. For each PCEP message type, a set of rules is defined that specify the set of objects that the message can carry. An implementation MUST form the PCEP messages using the object ordering specified in this document.

A PCEP LS Report message (also referred to as LSRpt message) is a PCEP message sent by a PCC to a PCE to report the link-state (and TE) information. A LSRpt message can carry more than one LS Reports. The Message-Type field of the PCEP common header for the LSRpt message is set to [TBD3].

The LS object is a mandatory object which carries LS information of a node or a link. Each LS object has an unique LS-ID as described in Section 9.3. If the LS object is missing, the receiving PCE MUST send a PCErr message with Error-type=6 (Mandatory Object missing) and Error-value=[TBD4] (LS object missing).

A PCE may choose to implement a limit on the LS information a single PCC can populate. If a LSRpt is received that causes the PCE to exceed this limit, it MUST send a PCErr message with error-type 19 (invalid operation) and error-value 4 (indicating resource limit exceeded) in response to the LSRpt message triggering this condition and SHOULD terminate the session.

If a PCEP speaker has advertised the LS capability on the PCEP session, the PCErr message MAY include the LS object. If the error reported is the result of an LS report, then the LS-ID number MUST be the one from the LSRpt that triggered the error.

The PCEP objects defined in this document are compliant with the PCEP object format defined in [RFC5440]. The P flag and the I flag of the PCEP objects defined in this document MUST always be set to 0 on transmission and MUST be ignored on receipt since these flags are exclusively related to path computation requests.

R (remote allowed - 1 bit): if set to 1 by a PCC, the R Flag indicates that the PCC allows reporting of remote LS information learned via other means like IGP and BGP-LS; if set to 1 by a PCE, the R Flag indicates that the PCE is capable of receiving remote LS information (from the PCC point of view). The R Flag must be advertised by both a PCC and a PCE for LSRpt messages to report remote as well as local LS information on a PCEP session. The TLVs related to IGP/BGP-LS identifier MUST be encoded when both PCEP speakers have the R Flag set.

Unassigned bits are considered reserved. They MUST be set to 0 on transmission and MUST be ignored on receipt.

Advertisement of the LS capability implies support of local link-state (and TE) distribution, as well as the objects, TLVs and procedures defined in this document.

The LS (link-state) object MUST be carried within LSRpt messages and MAY be carried within PCErr messages. The LS object contains a set of fields used to specify the target node or link. It also contains a flag indicating to a PCE that the LS synchronization is in progress. The TLVs used with the LS object correlate with the IGP/BGP-LS encodings.

Protocol-ID (8-bit): The field provide the source information. The protocol could be an IGP, BGP-LS or an abstraction algorithm. Incase PCC only provides local information of the PCC, it MUST use Protocol-ID as Direct. The following values are defined (some of them are same as [RFC7752]):

S (SYNC - 1 bit): the S Flag MUST be set to 1 on each LSRpt sent from a PCC during LS Synchronization. The S Flag MUST be set to 0 in other LSRpt messages sent from the PCC.

R (Remove - 1 bit): On LSRpt messages the R Flag indicates that the node/link/prefix has been removed from the PCC and the PCE SHOULD remove from its database. Upon receiving an LS Report with the R Flag set to 1, the PCE SHOULD remove all state for the node/link/prefix identified by the LS Identifiers from its database.

LS-ID(64-bit): A PCEP-specific identifier for the node or link or prefix information. A PCC creates an unique LS-ID for each node/link/prefix that is constant for the lifetime of a PCEP session. The PCC will advertise the same LS-ID on all PCEP sessions it maintains at a given times. All subsequent PCEP messages then address the node/link/prefix by the LS-ID. The values of 0 and 0xFFFFFFFFFFFFFFFF are reserved.

Unassigned bits are considered reserved. They MUST be set to 0 on transmission and MUST be ignored on receipt.

TLVs that may be included in the LS Object are described in the following sections.

In case of remote link-state (and TE) population when existing IGP/BGP-LS are also used, OSPF and IS-IS may run multiple routing protocol instances over the same link as described in [RFC7752]. See [RFC8202] and [RFC6549] for more information. These instances define independent "routing universes". The 64-Bit 'Identifier' field is used to identify the "routing universe" where the LS object belongs. The LS objects representing IGP objects (nodes or links or prefix) from the same routing universe MUST have the same 'Identifier' value; LS objects with different 'Identifier' values MUST be considered to be from different routing universes.

The format of the optional ROUTING-UNIVERSE TLV is shown in the following figure:

To allow identification of VPN link, node and prefix information in PCEP-LS, a Route Distinguisher (RD) [RFC4364] is used. The LS objects from the same VPN MUST have the same RD; LS objects with different RD values MUST be considered to be from different VPNs.

To realize ACTN, the MDSC needs to build an multi-domain topology. This topology is best served, if this is an abstracted view of the underlying network resources of each domain. It is also important to provide a customer view of network slice for each customer. There is a need to control the level of abstraction based on the deployment scenario and business relationship between the controllers.

Virtual service coordination function in ACTN incorporates customer service-related knowledge into the virtual network operations in order to seamlessly operate virtual networks while meeting customer's service requirements. [I-D.ietf-teas-actn-requirements] describes various VN operations initiated by a customer/application. In this context, there is a need for associating the abstracted link state and TE topology with a VN "construct" to facilitate VN operations in PCE architecture.

VIRTUAL-NETWORK-TLV as per [I-D.leedhody-pce-vn-association] can be included in LS object to identify the link, node and prefix information belongs to a particular VN.

As described in [RFC7752], each link is anchored by a pair of Router-IDs that are used by the underlying IGP, namely, 48 Bit ISO System-ID for IS-IS and 32 bit Router-ID for OSPFv2 and OSPFv3. Incase of additional auxiliary Router-IDs used for TE, these MUST also be included in the link attribute TLV (see Section 9.3.9.2).

It is desirable that the Router-ID assignments inside the Node Descriptor are globally unique. Some considerations for globally unique Node/Link/Prefix identifiers are described in [RFC7752].

The Local Node Descriptors TLV contains Node Descriptors for the node anchoring the local end of the link. This TLV MUST be included in the LS Report when during a given PCEP session a node/link/prefix is first reported to a PCE. A PCC sends to a PCE the first LS Report either during State Synchronization, or when a new node/link/prefix is learned at the PCC. The value contains one or more Node Descriptor Sub-TLVs, which allows specification of a flexible key for any given node/link/prefix information such that global uniqueness of the node/link/prefix is ensured.

The Remote Node Descriptors contains Node Descriptors for the node anchoring the remote end of the link. This TLV MUST be included in the LS Report when during a given PCEP session a link is first reported to a PCE. A PCC sends to a PCE the first LS Report either during State Synchronization, or when a new link is learned at the PCC. The length of this TLV is variable. The value contains one or more Node Descriptor Sub-TLVs defined in Section 9.3.6.

The sub-TLV values in Node Descriptor TLVs are defined as follows (similar to [RFC7752]):

Autonomous System: opaque value (32 Bit AS Number)

BGP-LS Identifier: opaque value (32 Bit ID). In conjunction with ASN, uniquely identifies the BGP-LS domain as described in [RFC7752]. This sub-TLV is present only if the node implements BGP-LS and the ID is set by the operator.

OSPF Area ID: It is used to identify the 32 Bit area to which the LS object belongs. Area Identifier allows the different LS objects of the same node to be discriminated.

Router ID: opaque value. Usage is described in [RFC7752] as IGP Router ID. In case this is not learned from IGP, it SHOULD contain the unique router ID, such as TE router ID.

The Link Descriptors TLV contains Link Descriptors for each link. This TLV MUST be included in the LS Report when during a given PCEP session a link is first reported to a PCE. A PCC sends to a PCE the first LS Report either during State Synchronization, or when a new link is learned at the PCC. The length of this TLV is variable. The value contains one or more Link Descriptor Sub-TLVs.

The 'Link descriptor' TLVs uniquely identify a link among multiple parallel links between a pair of anchor routers similar to [RFC7752].

The format and semantics of the 'value' fields in most 'Link Descriptor' sub-TLVs correspond to the format and semantics of value fields in IS-IS Extended IS Reachability sub-TLVs, defined in [RFC5305], [RFC5307] and [RFC6119]. Although the encodings for 'Link Descriptor' TLVs were originally defined for IS-IS, the TLVs can carry data sourced either by IS-IS or OSPF or direct.

The information about a link present in the LSA/LSP originated by the local node of the link determines the set of sub-TLVs in the Link Descriptor of the link as described in [RFC7752].

The Prefix Descriptors TLV contains Prefix Descriptors uniquely identify an IPv4 or IPv6 Prefix originated by a Node. This TLV MUST be included in the LS Report when during a given PCEP session a prefix is first reported to a PCE. A PCC sends to a PCE the first LS Report either during State Synchronization, or when a new prefix is learned at the PCC. The length of this TLV is variable.

This TLV is applicable for LS Prefix Object-Types for both IPv4 and IPv6.

This TLV is applicable for LS Link Object-Type. The format and semantics of the 'value' fields in some 'Link Attribute' sub-TLVs correspond to the format and semantics of value fields in IS-IS Extended IS Reachability sub-TLVs, defined in [RFC5305], [RFC5307] and [RFC7752]. Although the encodings for 'Link Attribute' TLVs were originally defined for IS-IS, the TLVs can carry data sourced either by IS-IS or OSPF or direct.

This TLV is applicable for LS Prefix Object-Types for both IPv4 and IPv6. Prefixes are learned from the IGP (IS-IS or OSPF) or BGP topology with a set of IGP attributes (such as metric, route tags, etc.). This section describes the different attributes related to the IPv4/IPv6 prefixes. Prefix Attributes TLVs SHOULD be encoded in the LS Prefix Object.

One of a key objective of PCEP-LS is to encode and carry only the impacted attributes of a Node, a Link or a Prefix. To accommodate this requirement, incase of a removal of an attribute, the sub-TLV MUST be included with no 'value' field and length=0 to indicate that the attribute is removed. On receiving a sub-TLV with zero length, the receiver removes the attribute from the database.

The main source of LS (and TE) information is the IGP, which is not active on inter-AS links. In some cases, the IGP may have information of inter-AS links ([RFC5392], [RFC5316]). In other cases, an implementation SHOULD provide a means to inject inter-AS links into PCEP. The exact mechanism used to provision the inter-AS links is outside the scope of this document.

This document extends PCEP for LS (and TE) distribution including a new LSRpt message with new object and TLVs. Procedures and protocol extensions defined in this document do not effect the overall PCEP security model. See [RFC5440], [RFC8253]. Tampering with the LSRpt message may have an effect on path computations at PCE. It also provides adversaries an opportunity to eavesdrop and learn sensitive information and plan sophisticated attacks on the network infrastructure. The PCE implementation SHOULD provide mechanisms to prevent strains created by network flaps and amount of LS (and TE) information. Thus it is suggested that any mechanism used for securing the transmission of other PCEP message be applied here as well. As a general precaution, it is RECOMMENDED that these PCEP extensions only be activated on authenticated and encrypted sessions belonging to the same administrative authority.

Further, as stated in [RFC6952], PCEP implementations SHOULD support the TCP-AO [RFC5925] and not use TCP MD5 because of TCP MD5's known vulnerabilities and weakness. PCEP also support Transport Layer Security (TLS) [RFC8253] as per the recommendations and best current practices in [RFC7525].

All manageability requirements and considerations listed in [RFC5440] apply to PCEP protocol extensions defined in this document. In addition, requirements and considerations listed in this section apply.

An implementation SHOULD allow the operator to view the LS capabilities advertised by each peer. To serve this purpose, the PCEP YANG module [I-D.ietf-pce-pcep-yang]" can be extended to include advertised capabilities.

An implementation SHOULD also provide the statistics:

Total number of LSRpt sent/received, as well as per neighbor

Number of error received for LSRpt, per neighbor

Total number of locally originated Link-State Information

These statistics should be recorded as absolute counts since system or session start time. An implementation MAY also enhance this information by recording peak per-second counts in each case.

An operator SHOULD define an import policy to limit inbound LSRpt to "drop all LSRpt from a particular peers" as well provide means to limit inbound LSRpts.

This document requests that a new sub-registry, named "LS Object Protocol-ID Field", is created within the "Path Computation Element Protocol (PCEP) Numbers" registry to manage the Flag field of the LSP object. New values are to be assigned by Standards Action [RFC8126].

Further, this document also requests that a new sub-registry, named "LS Object Flag Field", is created within the "Path Computation Element Protocol (PCEP) Numbers" registry to manage the Flag field of the LSP object.New values are to be assigned by Standards Action [RFC8126]. Each bit should be tracked with the following qualities:

The PCEP-LS protocol extension as described in this I-D were implemented and tested for a variety of applications. Apart from the below implementation, there exist other experimental implementations done for optical networks.

The PCEP-LS has been implemented as part of IETF97 Hackathon and Bits-N-Bites demonstration. The use-case demonstrated was DCI use-case of ACTN architecture in which to show the following scenarios:

- connectivity services on the ACTN based recursive hierarchical SDN/PCE platform that has the three tier level SDN controllers (two-tier level MDSC and PNC) on the top of the PTN systems managed by EMS.

- Integration test of two tier-level MDSC: The SBI of the low level MDSC is the YANG based Korean national standards and the one of the high level MDSC the PCEP-LS based ACTN protocols.

- Performance test of three types of SDN controller based recovery schemes including protection, reactive and proactive restoration. PCEP-LS protocol was used to demonstrate quick report of failed network components.

Huawei (PNC, MDSC) and SKT (MDSC) implemented PCEP-LS during Hackathon and IETF97 Bits-N-Bites demonstration. The demonstration was ONOS-based ACTN architecture in which to show the following capabilities:

Both packet PNC and optical PNC (with optical PCEP-LS extension) implemented PCEP-LS on its SBI and well as its NBI (towards MDSC).

SKT orchestrator (acting as MDSC) also supported PCEP-LS (as well as RestConf) towards packet and optical PNCs on its SBI.

Range |
---------------+---------------------------------------------
0 | Reserved - must not be allocated.
|
1 .. 255 | New PCEP sub-TLV allocated according to the
| registry defined in this document.
|
256 .. 65535 | Per BGP registry defined by [RFC7752].
| Not to be allocated in this registry.

This document creates a new registry for the PCEP-LS sub-TLVs (Section 13.6) and define new sub-TLV codepoints. Another approach could be to use the BGP-LS registry which is already defined for use in BGP. This is possible because the "BGP-LS Node Descriptor, Link Descriptor, Prefix Descriptor, and Attribute TLVs" registry marks 0-255 as reserved. Thus the space of the sub-TLV values for the Type field can be partitioned as shown below -

[Editor's Note - If this approach is agreed by the WG, the document would be updated with new sub-TLV type values.]

As per Hierarchical-PCE [RFC6805], Parent PCE builds an abstract domain topology map with each domain as an abstract node and inter-domain links as an abstract link. Each child PCE may provide this information to the parent PCE. Considering the example in figure 1 of [RFC6805], following LS object will be generated:

Further the exact border nodes and abstract internal path between the border nodes may also be transported to the Parent PCE to enable ACTN as described in [I-D.ietf-pce-applicability-actn] using the similar LS node and link objects encodings.